Triangulation for Autosomal DNA

In our last article, Triangulation for Y DNA, we covered triangulation for the Y chromosome, how it works, and how it can help a genetic genealogist.

In this article, we’re going to cover triangulation for autosomal DNA.

Triangulation for autosomal DNA is kind of a chicken and egg thing.  The goal is to associate and identify specific DNA segments to specific ancestors.  The easiest way to do this, or to begin the process, is with known relatives.  This gets you started identifying “family segments.”  From that point, you can use the known family segments, along with some common sense tools, to identify other people that are related through those common ancestors.  Through those matches with other people, you can continue to break down your DNA into more and more granular family lines.  This is easiest to visualize thinking about your 4 grandparents.

Triangulation is easiest if you have parents or grandparents living, and you can test them.  Yes, all of them.  Their DNA will give your immediate pointers when you have matches to which side of the family you share with your matches.  If you can test your 4 grandparents, you immediately know which of those 4 lines someone who matches you descends through, because they will also match one, and hopefully only one, of your 4 grandparents.  However, for some of us, testing even one parents is simply not possible, so first, let’s look at some examples of triangulation without your parents DNA results.

I’m fortunate that one of my cousins has given a lot of focus to our Vannoy line.  Vannoy was the surname of my great-grandmother, Elizabeth Vannoy (1846-1918) who married Lazarus Estes (1845-1919).  The Vannoy line has a mystery we’ve been trying to solve for decades now called, “Who Was Elijah Vannoy’s Father?”.  Elijah was Elizabeth’s grandfather.  Your family probably has a similar mystery, and these tools hold the potential to answer those questions.  They also have the potential to introduce more questions.  But then again, isn’t that the way of genealogy?  For every ancestor we find, we get two more questions.

Several of the Vannoy cousins are interested in solving this mystery as well, so they have taken the autosomal Family Finder test at Family Tree DNA.

We know how they are related, and the men have all been proven to be Vannoy via Y-line testing.  By doing this, we’ve assured no undocumented adoptions, also known as NPEs (NonParental Events) in the Vannoy line.

We expect our cousins to match, and indeed they do.  This is my test result showing my three cousins who match me.

In my family mystery, “Who Was Elijah Vannoy’s Father?”, there are 4 candidates, all brothers who lived in Wilkes County, NC in the late 1700s.  Elijah was born in 1786.  We have the wives surnames.  Hickerson is our primary candidate surname, so I wanted to see everyone who matches me on my match list who also shows the Hickerson surname.  I enter that surname in the “ancestral surname” box, and click on “run report.”  The matches returned will all carry the Hickerson surname, which you can see by scrolling for the highlighted names. Turns out, it was only my Vannoy cousins – today – but tomorrow might be different.

Vannoy match 1

Now for the triangulation tool.

I want to see if these three people share common DNA not just with me, but with each other.  If we all share a common segment of DNA, then that confirms a common ancestor and attributes the DNA at that address on that chromosome to that specific ancestral family.  This is the fundamental concept on which triangulation is based.

In my case, the known ancestral family is Vannoy, not Hickerson, at least not yet, so let’s look at the Vannoy cousins as compared to me.

vannoy match 2

Each of the participants results are color coded.  On the page below, you can see that each matching segment of the chromosomes is colored.  It turns out that all of us share a fairly large segment on Chromosome 15.  So now we can attribute that segment to Elijah Vannoy, our oldest proven ancestor in that line.  You can also see some areas where one or two of my cousins match my DNA, but not all of us.  Those can also be attributed to Elijah Vannoy’s line since we share no other (known) common ancestors.

vannoy match 3

This cousin match is simple because the men share the same surname, but if this was 3 women with different surnames, the matching would still work.  The challenge of course would be to find the common ancestor.  In this case, if all 3 women had Elijah Vannoy in their tree, we could still tell that this segment of Chromosome 15 was attributed to the Vannoy family because they all matched me and matched each other as well on the same DNA segment.

Eliminating False Matches

Now let’s move to the “what ifs.”  When my kids were young, I just hated sentences that started with “what if.”

What if I have a fourth match, Jane, with unknown ancestry who matches me on these segments, but does not match any of my cousins?

To determine this you would also have to look at your cousin’s matches or ask Jane if she also matches those cousins.  Remember that half of your DNA is that of your mother and the other half is that of your father.  You will have people that match you, and potentially on the same segments as your known relatives match you, but are not related to both you and your relatives.  This means they are matching you on the other half of your DNA.  In this case, if Jane didn’t match my Vannoy cousins too on that same segment of chromosome 15, then we would know that Jane’s match would be from my mother’s side.

To illustrate this point, let’s move to my results at 23andMe.

Let’s use Family Inheritance Advanced to see an example of two people who match me on the same segment, but are from opposite sides of my family.  My cousins Stacy and Cheryl are from Dad’s and Mom’s side of the family, respectively.  We know they don’t share common ancestry, but look, they both match me on four of the same segments.

cheryl stacy match

How is this possible, you ask.  Remember, I have two halves of each chromosome, one from Mom and one from Dad.  It just so happens that Cheryl and Stacy both match me on the same segment, but they are actually matching two different sides of my chromosome.  For this reason, these are called HIRs, or Half Identical Regions.

Now let’s prove this to the doubting Thomas’s out there.

cheryl stacy match 2

Here is the comparison of Cheryl and Stacy directly to each other.  They do have one small matching segment, 6 cM, so on the small side.  But they don’t match each other on any of the segments where I match both of them.

If they did match each other and me on the same locations, it would mean that we three have common ancestry.

The fact that they match each other on one segment could also mean they have distant common ancestry, which could be from one of our common lines or a line that I don’t share with them, or it could mean they have an identical by state (IBS) segment, meaning they come from a common population someplace hundreds to thousands of years ago.

The real message here is that you can never, ever, assume.  We all know about assume, and if you do, it will.  In this case, assuming would have been easy if you didn’t delve into the big picture, because both of these family lines contain Millers from Ohio living in close proximity in the 1800s.  However these Miller lines have been proven not to be the same lines (via Yline testing) and therefore, any assumptions would have been incorrect, despite the suggestive location and in-common names. Furthermore, cousin Stacy’s Miller line married into her line after our common ancestor, so is not blood related to me.  But conclusions are easy to jump to, especially for excited or inexperienced genetic genealogists.  It’s tempting even for those of us who are fairly seasoned now, but after you’ve been burned a few times, you do learn some modicum of restraint!

So, what’s next?

Color your Chromosomes

In my article, “The Autosomal Me – the Holy Grail – Identifying Native Genealogy Lines,” I described in detail the process of downloading your DNA information from either 23andMe or Family Tree DNA and then utilizing that information in a spreadsheet to look at matches – not 3 or 4 matches at a time, but chromosome by chromosome.

In my case, I was fortunate to have my mother’s DNA results at Family Tree DNA before she passed away, and I was equally as fortunate that they were still viable for the Family Finder test.  Believe me, I held my breath.

Because I have her results, I can tell immediately if my matches are from her side or from my father’s side.  If the person matches both Mom and me, then it’s from her side.  See how easy triangulation is.

Let’s take a look at Chromosome 15 with all of those Vannoy matches on my spreadsheet and see what kind of information we can glean.

vannoy table 1

On my master spreadsheet, my Mother’s matches have been copied in and are color coded, but since none of these people match Mother, I have eliminated that aspect here to avoid unnecessary confusion.

The people identified as “Dad” mean that I know they are genealogically related on my father’s side.  People who match Mother genetically are labeled Mom.  There aren’t any on this segment of chromosome 15, in our example above.  The blank cells in that column, by inference, match Dad’s DNA, since they don’t match Mom.  When I confirm genealogically how we’re related, I’ll enter “Dad” in that column, but not until then.

I’d like to comment on information gleaned from the spreadsheet.  Every DNA segment has a story to tell.

Cousin Estes

First, Cousin Estes, with yellow highlighting, is one of my closest Estes relatives.  He is a third cousin on the Estes side and also descends from Lazarus Estes and Elizabeth Vannoy.  He matches me on the segment from 26 (million) to 58 (million). My Vannoy group of matches, shaded green, extend from 33 to 58, so this tells me that the area from 26 to 33 where I match Cousin Estes, and not any Vannoys, is probably from an Estes ancestor, and not the Vannoy line.

Unfortunately, I don’t have any other matches on this segment, so I can’t figure out which line it comes from, just yet.

The green areas are common between me, cousin Estes and the Vannoy cousins.  If we could find a Hickerson match on these same segments, we could then solve the family mystery AND attribute part of this DNA to the Hickerson line.  But so far, no dice.  This is why it’s important to continue to look and to reach out to people you match, especially those who don’t enter their family surnames or post a GEDCOM file.  The answer may be waiting for you.

The Insanity Factor

The pink segment labeled Cousin Younger is making me insane, so let me share some insanity with you.

The Younger line descends through the Estes line, significantly upstream. The Y DNA of Marcus Younger, who had 1 son who had 1 son, does not match the expected Younger DNA line in Halifax County, Va.  Cousin Younger’s only solid Y match also doesn’t match his expected family line, so we’re fish out of water on the Y-line.  Two undocumented adoption cases that match each other, but no one else.  Great, just great.  These are the things genetic genealogy nightmares are made of.

Mary Younger, daughter of Marcus Younger, married George Estes who fought in the Revolutionary War.  Their son John R. Estes married Nancy Ann Moore in Halifax County and they settled in Claiborne County, TN about 1820 where the Vannoy family is found as well, having migrated from Wilkes Co., NC.  John Y. Estes, son of John R. Estes had son Lazarus Estes who married Elizabeth Vannoy.  Here’s the generational progression:

  1. Marcus Younger – wife unknown, Y DNA doesn’t match Younger line
  2. Mary Younger married George Estes, Halifax Co., VA
  3. John R. Estes married Nancy Ann Moore, moved to Claiborne Co, TN
  4. John Y. Estes married Rutha Dodson
  5. Lazarus Estes married Elizabeth Vannoy
  6. George Estes married Ollie Bolton
  7. My father, William Sterling Estes

And of course, there’s a monkey-wrench, so let’s throw it in.  Marcus Younger’s grandson, ancestor of Cousin Younger, married a Moore woman in Halifax County, VA.  We believe we know who her parents are, but we’re not positive.  If they are who we believe, Y-line DNA tests say the 2 Moore families, living within sight of each other, aren’t the same Moore line….but they interact closely and my Moore line doesn’t match any Moores upstream anyplace.  So, we have another unknown ingredient in the soup.

So, from me, Marcus Younger is 7 generations upstream.  I should carry about 1.5% of his DNA.  I was pleased to see that my Younger cousin and I matched.

However, and this is a BIG however, the Vannoy line should not be related to the Younger line.  We know that both of these cousins are matching on my father’s side, not just because of the genealogy, but because neither matches my mother.  But they are somehow related, as Cousin Younger is matching the Vannoy group big as life on chromosome 15.  Could this be an IBS (identical by state) segment?  Yes, it’s small – but I’m not comfortable relegating it to IBS because it’s genealogically “inconvenient,” at least not yet.

So, something may well be wrong, amiss or unknown in the genealogy, either in Tennessee, which is doubtful as we have that fairly solidly nailed down, especially in recent generations, or in Virginia where there is at least one known disconnect and possibly two taking into consideration the Moore monkeywrench.  Still, the Vannoy family was not living in the same state as the Younger family and came from New Jersey to North Carolina, not from Virginia.  Maybe the connection is in one of the unknown wives lines.

So, you can see my reason for being perplexed.  One thing is sure.  DNA doesn’t lie.  It’s up to us to figure out the message it is conveying and which ancestor it is from.

Powerful Tools

I hope you can see what a powerful tool we have at our disposal.  Of course, it can reveal who your ancestors are, along with some surprises.  I don’t mind the surprises.  I view them as gifts from the ancestors.  It’s those crazy-making half-surprises that bother me.  I swear, the ancestors have a sense of humor.

55 thoughts on “Triangulation for Autosomal DNA

  1. For whatever it’s worth, there is a Vannoy who owns a chain of tire stores here in Pensacola, FL. Name is “Vannoy’s Tires.” Maybe he has a clue for you?

  2. Roberta,
    I posted this on 23andme but I thought you might know. Is there a program that allows one to create a master graph of our chromosomes. I would like on the Chromosome Mapping Tool (CMT)

    It starts with a blank graphic representation of all 23 pairs of chromosomes each having a top and bottom bar.

    There is a color coded KEY which you select the color and then type in one of your 16 great great grandparents to represent the color you select.

    Then there is an entry form where you enter a chromosome, start and stop points and select a color ( representing a GG grandparent) and it paints that on your Chromosome Map. I would suggest all maternal lines in a warm color: Magenta, Red, Pink, Orange, Melon, Yellow, Ochre and Tan. Paternal Lines in Navy, Royal, Sky, Lime, Forest, Grass, Purple, Lavender.

    If you know of how to do this easily or someone who has created an app I’d much appreciate it. If not do you know anyone who could?
    Kelly Wheaton

  3. Would it be possible to triangulate using my maternal uncle’s autosomal DNA since my parents have both passed on? I was not sure if you have done a blog on that subject. I am guessing that my mother’s dna would match my uncle’s DNA since he matches me on those segments.

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  6. Hello, Really enjoy this subject being explained. I have a question does it matter which Chromosome you match on say you all match with a large segment on Chromosome 2? Is there a meaning to which of the 22 chromosome you match on? This is what I mean if you match on 2 does that mean you match at generation 2? Having a hard time figuring out Chromosome matching.

    • No, the chromosome numbers are arbitrary and have nothing to do with generations. The key is matching on the same segment of the same chromosome with another person. Generations are figured by both 23andMe and Family Tree DNA based on how much DNA you share.

  7. Roberta,
    Thanks for directing me to this article. It really touched base with me as my brick wall involves my 2nd gr grandfather and “Who is the father?” The choices involve 4 brothers as well. I have developed my tree to include descendants of all the brothers and am starting to contact them for DNA analysis. One brother in particular is suspect as I have received no less than 20 autosomal matches to researchers of this brother’s wife’s line. I try not to jump to conclusions, but it is so hard. I can’t wait to gt started “painting”.

    Also, I appreciate your directing me to the XDNA article posted by Jim. I had completely ignored this is gedmatch because I didn’t think it would apply to me. I have contacted a couple of matches here as well.

    David

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  9. I am 100% Ashkenazi Jew. My paternal first cousin matched me exactly on mtDNA. I tried to use Family Finder as follows: a) found all matches NOT in common with my cousin and assumed these are from maternal side; b) sorted the ones in common and selected only those on top. There are three such, one came on both as a 3rd cousin and other two came as 3-4 and 4-3.
    Chromosome browser came with shared segments on one crhomosome for all four people, but the amounts (obviously except my 1st cousin) are below 10cM.

    I do know ALL my second cousins and most of my third cousins (since I know all my great grandparents and in most cases their siblings). There are several great grandparents I do not know siblings so that was the major reason to go to DNA — to find some 3rd or 4th cousins. I am starting to have MAJOR doubts whether for Jews this type of search is actually at all possible.
    I have a first cousin on my maternal side tested, also some 2nd and will see how triangulation works there. But again, I am not very hopeful. Please provide your feedback…
    Thanks
    Luc

    • I am not an expert in Jewish autosomal DNA. I do know that often Jewish matches “appear closer” in time because they share a lot of DNA not because they are directly related, but because they have intermarried for generations and share a lot of the same DNA as a population. I don’t know whether you’ll be able to do this or not either, but I’d surely be interested in what you find.

  10. LOL. This is what I have been doing all along..just didn’t realize the name ‘traingulation’ was the correct ‘terminology’ for what I was doing..and here I thought I was missing something! LOL Well, better to try to keep learning… :)
    Thx–great explanation! I’ll be passing this one along Roberta as you did an excellent job explaining this concept! :)

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  12. My brother has a 3rd cousin male Autosomal match. I, female, share no segments, Autosomal or X-chromosome, with my brother’s cousin according to GEDmatch and FTDNA. However, when I compare the 3 of us using the FTDNA Chromosome Browser, my brother’s cousin and I share some significant segments with my brother. Please, can you explain?

    • In order to compare using the chromosome browser, you must have a match. The only way you can use the browser to compare people is if they match with you. If you’re using your brother’s browser, and you both match to him, then the 3 of you can compare. You can drop the threshold below the 7cM match threshold, and you likely share segments there.

  13. Yep, I’m comparing my brother who of course matches with both of us. So, does having shared segments with my brother’s cousin (even though the two of us don’t share any segments) mean that we have a common ancestor some where down the line or should I just ignore?

  14. Recently my Aunt, Uncle and Cousin did DNA testing at FamilyTrees. The results are mostly in and I am confused. They all show with the correct relationship on the autosomal results. But, my cousin shows as a distance of 1 on the mtDNA to both me and her mother while I, my Aunt and my Uncle have a distance of 0. How can I show a closer match to her mother than she does. The autosomal confirms her mother as her mother which I know to be true. Obviously there is something I do not understand.
    Thank you.

      • My cousin and I share a match on GEDMatch at both one on one autosomal and with a chromosome match. We then matched ours with many, and came up with several that matched us both on autosomal, but not a chromosome match. What does that mean exactly?

      • If I understand what you are saying, it means that you do match, but not on the same chromosome. Because of that, you can’t confirm that you share a common specific ancestor with others. However, you two may have matches that match both of you and also on the same chromosome, so don’t give up.

  15. I would like to make sure i understand this correctly, anyone i match on a specific chromosome means that we share the same ancestor-or does it have to be on the same segment on that chromosome? Thank you!

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  17. Roberta wrote:

    <This cousin match is simple because the men share the same surname, but if this was 3 women <with different surnames, the matching would still work. The challenge of course would be to find <the common ancestor. In this case, if all 3 women had Elijah Vannoy in their tree, we could still <tell that this segment of Chromosome 15 was attributed to the Vannoy family because they all <matched me and matched each other as well _on the same DNA segment_.

    What if I have 3 matches who all match me and match each other in FTDNA’s Family Finder Matrix but the most distantly related cousin doesn’t match me _on any parts of the same DNA segments_ where I match the other 2?

    THE KNOWN FACTS: A mother-daughter pair (my 2nd cousin once removed and my 3rd cousin, respectively) share fairly large segments with me on 3 different chromosomes. We know from our paper trail that our MRCAs are a pair of my 2nd-great-grandparents. Those 2 cousins and I all match a more distant cousin in the Matrix (my 3rd cousin once removed, who descends from my 2nd-great-grandfather’s _brother_). So the more distant cousin shares my 2nd-great-grandfather’s _parents_ as the MRCAs with my closer cousins and me but does not share my 2nd-great-grandmother’s line. That 3rd cousin once removed does not share any parts of the segments that my 2 closer cousins and I share. Likewise, those 2 closer cousins (the mother-daughter pair) don’t share any parts of the rather small segments that I share with my 3rd cousin once removed. All of us have sufficiently complete family trees to be reasonably sure we don’t have any other lines in common, going back as far as the MRCA generations.

    QUESTIONS: What can we infer from that?

    Does the fact that I match the 2 closer cousins and the more distant one on mutually exclusive segments indicate that the segments where I match the closer cousins came from my 2nd-great-grandmother, who isn’t biologically related to the more distant cousin?

    Or something else?

    Or does the randomness of recombination make it impossible to tell without testing additional cousins?

    Many thanks for any clarification you can provide.

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  21. Hello Roberta,
    Ive tested my daughter now I’m testing a potential half aunt to see if her brother is my daughters father. How much cms would be linked to them? Using the autosomal test.

  22. Can someone help me figure this out? I have a predicted 4th cousin on 23andme/Ancestry, we both share a predicted 3rd cousin (closest to both of us) on Ancestry, does this mean all three of us share the same great great grandparent?

    • The problem is that Ancestry gives you no tools to figure that out, so you can’t see if you match on the same segments and you have no way of knowing if your genetic connection to that person is through that ancestor. If the genealogy is right, and if the connection to that person is from that ancestor, then yes, it would mean you share a common ancestor, but you can’t take the estimates of which ancestor as exact. Those estimates are made assuming you receive exactly 50% of your ancestor’s DNA in each generation and that isn’t accurate, but it’s the only way of estimating that we have. You can download everyone’s raw data files to Gedmatch and compare and that might be helpful.

      • oh ok i see, i sure hope we can figure it out. Me and the 4th cousin are already on denmatch, how can i downloadthe 3rd cousins raw date there? Or would they have to do it themselves?

      • Hello, since my last question, our 3rd cousin match has uploaded on gedmatch. We all share on ch. 16 and they match each other on a couple other chromosomes as well. My 4th cousin and this 3rd cousin of mine (that match each other as 3rd cousins also ) are around the same age. Does it appear that I am a 3rd cousin once removed to this 3rd cousin of ours?..if so why Is my 4th cousin a third cousin to her also? I am confused on all this! I can’t tell who our common ancestor might be?

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